Characterizing the interaction between the bogus yucca moth and yuccas: do bogus yucca moths impact yucca reproductive success?

Abstract

Yucca moths are most well known for their obligate pollination mutualism with yuccas, where pollinator moths provide yuccas with pollen and, in exchange, the moth larvae feed on a subset of the developing yucca seeds. The pollinators, however, comprise only two of the three genera of yucca moths. Members of the third genus, Prodoxus, are the "bogus yucca moths" and are sister to the pollinator moths. Adult Prodoxus lack the specialized mouthparts used for pollination and the larvae feed on plant tissues other than seeds. Prodoxus larvae feed within the same plants as pollinator larvae and have the potential to influence yucca reproductive success directly by drawing resources away from flowers and fruit, or indirectly by modifying the costs of the mutualism with pollinators. We examined the interaction between the scape-feeding bogus yucca moth, Prodoxus decipiens, and one of its yucca hosts, Yucca filamentosa, by comparing female reproductive success of plants with and without moth larvae. We determined reproductive success by measuring a set of common reproductive traits such as flowering characteristics, seed set, and seed germination. In addition, we also quantified the percent total nitrogen in the seeds to determine whether the presence of larvae could potentially reduce seed quality. Flowering characteristics, seed set, and seed germination were not significantly different between plants with and without bogus yucca moth larvae. In contrast, the percent total nitrogen content of seeds was significantly lower in plants with P. decipiens larvae, and nitrogen content was negatively correlated with the number of larvae feeding within the inflorescence scape. Surveys of percent total nitrogen at three time periods during the flowering and fruiting of Y. filamentosa also showed that larval feeding decreased the amount of nitrogen in fruit tissue. Taken together, the results suggest that although P. decipiens influences nitrogen distribution in Y. filamentosa, this physiological effect does not appear to impact the female components of reproductive success.

Experimental analysis of constitutive and induced defence in a plant–seed–predator system

“…Unfortunately, our results do not allow us to establish whether this was due to (i) a change in resource allocation in response to exposure (change in seed provisioning as measured in fruits produced after exposure to larval attack), or (ii) differences among plants in nutritional quality and suitability for the larva. An effect on resource allocation has been observed in the Yucca–Yucca Moth system, where feeding by larvae decreased the amount of N in seeds and fruit tissue (Althoff, Segraves & Sparks 2004). In the second case, which assumes that the early fruits consumed by the larvae had the same composition as the late fruits, H. bicruris larval growth should be dependent on a higher C : N ratio in the diet (Althoff et al .…”

“…An effect on resource allocation has been observed in the Yucca–Yucca Moth system, where feeding by larvae decreased the amount of N in seeds and fruit tissue (Althoff, Segraves & Sparks 2004). In the second case, which assumes that the early fruits consumed by the larvae had the same composition as the late fruits, H. bicruris larval growth should be dependent on a higher C : N ratio in the diet (Althoff et al . 2004).…”

The role of ecological availability and host plant characteristics in determining host use by the bogus yucca moth Prodoxus decipiens

“…The bogus yucca moth, P. decipiens , is an internally feeding herbivore of five Yucca species that occur in eastern North America: Yucca aloifolia , Yucca constricta , Yucca filamentosa , Yucca glauca and Yucca glauca arkansana . The moth's entire life cycle is tied to its host plant (Riley, ; Althoff et al , ). Moths eclose during the flowering season of the host plants.…”

“…The moth's entire life cycle is tied to its host plant (Riley, 1892;Althoff et al, 2004). Moths eclose during the flowering season of the host plants.…”

Limiting the success of stem borers (Prodoxus quinquepunctellus) in yuccas: indirect effects of ants, aphids, and fruit position

“…Prodoxus has higher survivorship in stalks that retain at least one fruit, and larger fruit sets increase the probability that fruit will be retained higher on the stalk, which also increases survivorship. Prodoxus decipiens feeding in the stalk of Yucca filamentosa had no effect on the final fruit set (Althoff et al , 2004), supporting the idea that yuccas and Prodoxus have a commensalistic relationship.…”